According to workers at the Brazilian government-run national Indian foundation, FUNAI, late last week a group of men from a paramilitary faction from Peru, armed with rifles and machine guns, entered Brazilian territory and encircled a remote jungle guard post used by FUNAI researchers to study and protect isolated indigenous tribes near the border with Peru.

The incident happened at a FUNAI post known as Xinane, a very remote monitoring location in Brazil's Acre state that serves as a small, five-person research base for the study and protection of isolated indigenous tribes in the region.

FUNAI officials say the armed men were most certainly trying to kill Indians in the area to make way for illegal logging, or new cocaine trafficking routes through the forest from Peru.

Either way, it represents a new escalation of threats of violence against Indians and those serving to protect them in a region along the Brazil-Peru border that has some of the highest concentration of isolated and uncontacted tribes anywhere in the world. (More here from Survial International about the uncontacted Indians of Brazil).

The armed men apparently hid in the forest surrounding the FUNAI outpost. The five workers on site saw it as an obvious threat and reported feeling vulnerable in the jungle area with little protection; the nearest Brazilian town being more than 200km away.

The FUNAI workers on site - which included Jose Carlos Meirelles, an indigenous peoples researcher with decades of experience in the region, as well as Carlos Travassos, the chief of the isolated Indians division of FUNAI – sent urgent emails from a satellite internet hookup to journalists, friends, and family alerting them to the situation.

In one email, according to Folha de Sao Paulo newspaper, Travassos reportedly said: “We are totally surrounded. They (the gunmen) are divided into three flanks. We have nowhere to run.”

Altino Machado, a local journalist in the city of Rio Branco, Brazil and one of the first to report on the incident on his blog and another blog he contributes to Terra Amazon Blog, also posted an email from Meirelles which said, in part: “Time in front of our computer is short. It’s not easy keeping one eye on the (computer) and the other on the Peruvian (gunmen)… (The gunmen) are still here…they are monitoring us and we are them.”

Late last week, Brazil’s federal police with the help of a military helicopter reportedly swooped in to evacuate the workers temporarily. But fearing the indigenous tribes would be massacred without their presence, the researchers flew back a short time later in a helicopter with police escorts only to find their base camp looted, signs that violence against Indians might have occurred.

Tiao Viana, the governor of Acre state, has reportedly deemed the situation so critical that he has asked federal authorities for more security to protect the FUNAI workers tasked with monitoring the welfare of the Indians.

Below: My report from 2008 with Jose Carlos Meirelles, now one of the indian researchers under threat:

The rising tensions come just weeks after Brazil announced a new, nationwide plan, to be led by the military, to beef up security along the16,000 kilometers of border Brazil shares with 10 other countries. The plan calls for 5,000 soldiers from the Army, backed by unmanned surveillance aircraft, to be placed at five strategic points to choke off drug trafficking.

But it's a monumental task. The Brazilian state of Acre, where the most recent incident took place and where the high concentration of uncontacted tribes is located, shares almost 900km of thick jungle border with Peru, a country quickly becoming a world leader in export of drugs, much of which comes through the Brazilian Amazon before being exported abroad.

But there is even more to this story.

Meirelles, one of the men encircled by the gunmen, was the man who led the expedition in 2008 that captured dramatic photos of uncontacted tribes that gained worldwide media attention.

The incident with the gunmen late last week occurred near the same general regional of the Amazon where those photos in 2008 were taken.

Travassos, of FUNAI, has said it's well known that Peruvian 'mercenaries' work for loggers and drug traffickers in the area. He said he thinks the gunmen were conducting "raids" to kill the Indians, which they view as obstacles to logging and lucrative drug trafficking routes. The gunmen likely threatend the FUNAI workers in the post as a way to intimidate the Brazilian authorities to abandon their work.

And the news in June of this year of the photos of other isolated Amazon tribes also was in the same general region (see my video report about this discovery here).

Travassos and Meirelles said they are planning to fly over the areas to get a better sense if the isolated tribes were harmed; but there is real concern some of the Indians might have been harmed.

In 2008, just days after the now famous photos were released, I flew to Feijo, Brazil and interviewed Meirelles in his modest wooden home he lives in while not in the jungle. At the time he told me he was very worried about illegal loggers from Peru encroaching into Brazilian territory, and the extreme risk that put on native peoples.

“There is massive logging on the Peru side of the border and unfortunately the Peruvian Amazon is a ‘no man’s land’ and everything is permitted,” he told me. “So the Indians are being displaced into Brazil.”

Ironically, back in 2008, Meirelles told me something urgently needed to be done before gangs of armed men from Peru started coming into Brazil to kill the Indians that "got in the way" of logging or drug trafficking.

Based on the worrisome developments of the past few days, Meirelles premonition could, sadly, be coming true.

But despite the apparent dangers, the team from FUNAI seems determined to stay at the outpost. In another email reported by the journalist Machado, Meirelles typed:

We will remain here…until the Brazilian government decides to resolve this absurd (situation)….Not for our protection. For the protection of the Indians!”

When there are new developments on the situation, I will post to my Twitter feed @elizondogabriel